Hydrocarbon oil treating process



ted S es Pmn This invention relates to the treatment of hydrocarbon distillate oils, particularly to the removal of mercaptans therefrom.

It is known to treat hydrocarbon oils, particularly gasoline and kerosene, with an aqueous hypochlorite solution such as sodium or calcium hypochlorite solution in order to oxidize the mercaptans present in the hydrocarbon oil and also, if desired, to reduce the sulfur content of the hydrocarbon oil.

Treatment of hydrocarbon oils with a hypochlorite solution for the removal of mercaptans often has the drawback that organo-sulfur-chlorine compounds are formed, especially sulfenyl chlorides and sulfonyl chlo rides, which, in the presence of water, cause the hydro- 7 carbon oil to be corrosive towards metals, especially iron and steel. While the corrosive compounds can be removed by treating the hydrocarbon oils with an alkali metal hydroxide solution, this treatment proceeds too slowly for practical purposes.

Ptented Deo 2,

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hypochlorite-treated oil, it has also been found that even better results are obtained when both' phenolates and mercaptans (or corresponding mercaptides) are presentduring the contacting of the hypochlorite-treated oil-with an alkali metal hydroxide solution. The combined pres ence of these results in a still greater reduction of the time of contact necessary for the removal of the corrosive compounds.

Mercaptides may be aded to the alkali metal hydroxide solution as such or in the 'form of mercaptans. However, it is preferred to contact the alkali metal hydroxide 'solution with a hydrocarbon oil which contains mercaptans but which is free from hydrogen sulfide. Mercaptans will then pass into the alkali metal hydroxide solution and are converted therein into the corresponding mercaptides. An even more convenient and effective ilmethod is to contact the hypochlorite-treated hydrocarbon oil at the same time with thephenolate-containing alkali metal hydroxide solution and a hydrocarbon oil containing mercaptans. The hydrocarbon oil containing mercaptans which is preferably used is one of the same o'rigin as the hypochlorite-treated hydrocarbon oil. In

T bon oil is added, in the presence of an alkali metal hyof' the invention a much larger concentration of phenolat'es is necessary than would result from the mere contacting of i the alkali metal hydroxide solution with the mixture of The principal objectof this invention is to provide an improved process for manufacturing sweetened hydrocarbon oils, especially those boiling in the boiling ranges of gasoline and kerosene. Another object is to provide an improved process for manufacturing a hypochloritetreated hydrocarbon oil which is not corrosive towards metals, especially iron and steel. Still another object is to provide such an improved process wherein the presence of small quantities of corrosive organo-sulfur-chlorine compounds in the treated oil is avoided in an inexpensive and expeditious manner.

It has now been found that the corrosive compounds present in a hypochlorite-treated hydrocarbon oil may be removed in a rapid and simple way by contacting the hypochlorite-treated hydrocarbon oil with an aqueous alkali metal hydroxide solution which contains one or more phenols, i. e., phenol, cresols or xylenols (in the formof the corresponding phenolates) in a quantity of at least 25 grams per liter, and preferably in the presence of an amount of mercaptans and/or the corresponding alkali metal mercaptidesequal to from about 5 to about 100 mol percent of the amount of mercaptans originally in. the hypochlorite-treated oiliv The term phenols or phenolates is meant to include both unsubstituted phenol or phenolate and alkyl phenols or alkyl phenolates. The technical mixture of cresols, often referred to as cresylic acids, is preferably used for carrying out the process according to the invention. For best results, it is prefthis case the process then amounts to the simple splitting of a mercaptan-containing hydrocarbon oil into two parts, one part 0-1 which is treated with hypochlorite solution, while after this treatment the other part of the hydrocardroxide solution containing *phenolates, to the first part.

Some sour hydrocarbon oils contain not only mercaptans but also small concentrations of phenolic compounds.

However, it has been found that to obtain the advantages the hypochlorite-treated part of the oil and the part of the sour oil which is not hypochlorite-treated. Thus, it

' is essential to add phenols (or phenolates) from an erable to use a solution of at least 50 grams of phenols, or a correspondingamountof phenolates, per liter of alkali metal hydroxide solution. The concentration of the phenol should not .be greater than about 700 grams per liter and preferably not greater than 500 grams per literof alkali metal hydroxide solution.-

While the presence of the phenolates in the alkali metal hydroxide solution -is remarkably efiective in promoting the removal of the corrosive compounds from the.

extraneous source.

The lower limit of mercaptans or mercaptid es added 7 to the mixture of hypochlorite-treated oil and phenolatecontaining alkali metal hydroxide solution depends upon the speed with which it is desired to carry out the removal of the corrosive compounds. The upper limit of the amount of mercaptides or mercaptans added depends upon the amount of mercaptans which can be tolerated in the final hydrocarbon oil to be obtained. Usually the requirement is that a hydrocarbon oil should give a negative doctor test, i. e., that the mercaptan sulfur content of the hydrocarbon oil should be 0.0005 by weight or less. In the usual case especially good results will be r obtained when the amount of mercaptans or correspond ing mercaptides added to the hypochlorite-treated oil is from about 5 to mol percent, more especially from about 10 to about 30 mol percent, of the mercaptans originally present in the oil which is hypochlorite-treated.

A When the source of the mercaptans is the originaloil,

and the oil is split into two parts as before mentioned,

the amount of the part of" the oil by-passed around the 4 hypochlorite treatment is therefor from about 5 to about 100 percent, more especially from about 10 to 30 percent, of the part of the oil which is hypochlorite-treated.

The process according to the invention is applicable with especially good results to both heavy hydrocarbon I distillate oil fractions, such as gas oil, and to light hydrocarbon oil fractions, such as gasoline, and particularly kerosene. It is generally applicable to hydrocarbon distillates having final boiling point no greater than about 700 F. The'preferred hydrocarbon oils are those which are substantially non-olefinic, for example, straight-run hydrocarbon oil distillates. A I m In the process of the invention, the presence of hydrogen sulfide oralkali metal sulfide is to be avoided both during the hypochlorite treatment and during the after treatment with the phenolate-containing alkali metal hy droxide solution. This is because sulfied sulfur reacts with hypochlorite, and generally also with the corrosive organo-sulfur-chlorine compounds such as sulfonyl chlorides, to form free sulfur which degrades the hydrocarbon oil product and which can be removed only with great difficulty and expense. Also, it is preferred that there be no methyl mercaptan or the corresponding merc'aptide present during either the hypochlorite treatment or the after-treatment, because in either case dimethyl disulfide is formed and remains in the treated hydrocarbon oil. This is an evil-smelling compound and would make the hydrocarbon oil commercially unacceptable for most uses. Accordingly, the sour hydrocarbon oil to be treated according to the invention should be first freed of hydrogen sulfide, for example, by a pre-treatment with alkali metal hydroxide solution, and preferably also freed of methyl mercaptan. A preferred form of the invention thus encompasses eliminating all components of the sour hydrocarbon oil feed boiling below 25 C. (that is, 25 C. in the unmixed state), for example, by conventional distillation. The resulting sour oil is then particularly suitable for processing according to the preferred technique, described above, wherein the sour feed is split into two parts, one being hypochlorite-treated and the other being by-passed to the after-treatment with phenolate-containing alkali metal hydroxide solution.

The concentration of alkali metal hydroxide in the aqueous solution with which the hypochlorite-treated oil is contacted is preferably from about 10% to about 30% by weight but may be as low as 3% or as high as 50% by weight. An aqueous sodium or potassium hydroxide solution is preferably used. The amount of alkali metal hydroxide' solution used is generally from about 5 to about 50% by volume and especially to 20% by volume, calculated on the total quantity of hydrocarbon oil, e. g., both the hypochlorite-treated oil and the mercaptan-containing oil when the latter is used.

It is desirable that the potential acid number of the hydrocarbon oil finally obtained should be 0.01 or less. By potential acid number is meant the number of milligrams of KOH which must be added in an alcoholic medium, per gram of hydrocarbon oil in order to saponify or neutralize the acid material, e. g., the sulfenyl and sulfonyl chlorides, present in the hydrocarbon oil.

If after the treatment according to the invention small amounts of corrosive compounds are still present in the hydrocarbon oil, the corrosive efiect thereof may be counteracted by adding to the hydrocarbon oil a small quantity, particularly from about 0.001 to about 0.1% by weight, of a substituted or unsubstituted aliphatic or cycloaliphatic monocarboxylic acid having 12 or more carbon atoms, the water-solubility of which is not more than 0.1 gram per liter at 20 C., e. g., oleic acid.

The hypochlorite treatment may be carried out by any of the known methods. A treatment with an aqueous alkaline sodium or calcium hypochlorite solution is preferred. Suitable aqueous solutions, for example, are those containing from about 0.1 to about 5% by weight, and especially 0.3 to 1% by weight of NaOCl, as well as from about 1 to about 30% by weight, and particularly 2 to 10% by weight, of NaOH. These solutions may also contain NaCl, usually in a quantity of l to 25% by weight, and especially 1 to 5% by weight. The process according to the invention is especially beneficial in those cases in which the hypochlorite solution used contains no or virtually no free hydroxide, so that many corrosive compounds are formed.

The quantity of the hypochlorite solution with which the hydrocarbon oil is brought into contact can vary. within wide limits. In general, the hypochlorite solution is used in excess with respect to the quantity which is theo retically (i. e., stoichiometric'ally) equivalent to the metcaptans present in the hydrocarbon oil which is hypochlorite treated, based on the oxidation of the mercaptans to disulfides. Satisfactory results are obtained if the amount of hypochlorite solution contacted with the hydrocarbon oil is from 3 to 15 times, particularly 5 to 10 times, the stoichiometric amount.

The invention is illustrated with reference to the following example.

. EXAMPLE A Middle East kerosene with a mercaptan sulfur content of 0.0152% by weight was treated for 5 minutes at room temperature with an alkaline hypochlorite solution (1 N NaOH, 0.1 N NaOCl) in a raito of 5 mol of NaOCl to 1 mol of mercaptan. The potential acid number of the kerosene treated was 0.030.

This kerosene was then treated with 10% by volume (based on the volume of the hypochlorite-treated kerosene) of aqueous solution containing 2 mols (292 grams) of potassium cresylate and 4.5 mols of KOH per liter. After 15 minutes the potential acid number of the kero sene had fallen from 0.030 to 0.002.

On addition of 35% by volume (based on the volume of the hypochlorite-treated kerosene) of the original kerosene together with 10% by volume of the same aqueous solution asreferred to above, the same hypochlorite-v Table I Hypochlorite- Hypochloritetreated kerotreatedkerosene +35% sene by vol. of

original kerosene Mereaptan sulfur content, percent by Nil 0.0032

weight.

Treated with 10% by vol. of aqueous solution containing, per liter, 2 mol of potassium cresylate and 4.5 mol of KOH.

Potential acid number:

For the purpose of comparison, the same experiment was carried out, using an alkali metal hydroxide solution containing alkali metal mercaptides. In this case a reaction time of 1 to 2 hoursis necessary in order to reduce the potential acid number to a level of from 0.001 to 0.002.

We claim as our invention:

1. A process for reducing the corrosivity of a hypochlorite treated hydrocarbon oil distillate containing acidic organo-sulfur-chlorine compounds which comprises preparing a treating solution by adding a phenol to an aqueous alkali metal hydroxide solution in an amount to produce a solution containing from about 25 to about 700 grams of phenol per liter of solution and contacting said distillate with said solution.

2. A process for producing a substantially non-corrosive doctor sweet hydrocarbon oilwhich comprises,

preparing a treating solution by adding a phenol to an aqueous alkali metal hydroxide solution in an amount to produce a solution containing from about 50 to about 500 grams of phenol per liter of solution, separately hypochlorite-treating a sour hydrocarbon oil distillate and then contacting the treated distillate with said treating solution. 7

3. A process in accordance with claim 2, whereinth hypochlorite-treated distillate is contacted with the alkali metal hydroxide solution containing a phenol in the presence of an amount of mercaptans of from about 5 to about 100 mol percent baseC. on the original mercaptan content of the sour distillate which is hypochloritetreated.

4. A process for producing a substantially non-corrosive doctor sweet hydrocarbon oil from a mercaptancontaining hydrocarbon oil distillate which comprises: (1) eliminating from the mercaptan-containing distillate those components having boiling points below 25 C.; (2) splitting the resulting distillate, still containing mercaptans, into a first part and a second part, the second part being from 5 to 100% of the first part; (3) contacting the first part with an aqueous hypochlorite solution in an amount in excess of the stoichiometric amount for the oxidation of the mercaptans therein to disulfides; (4) separating the resulting hygrochlorite-treated first part; (5) mixing this treated first part with the second part and also with an aqueous alkali metal hydroxide solution containing from about 50 to about 500 grams of a phenol per liter of solution; and (6) separating the distillate from the aqueous solution.

Earhart Oct. 18, 1955 Le Nobel et a1. Oct. 9, 1956 

1. A PROCESS FOR REDUCING THE CORROSIVITY OF A HYPOCHLORITE TREATED HYDROCARBON OIL DISTILLATE CONTAINING ACIDIC ORGANO-SULFUR-CHLORINE COMPOUNDS WHICH COMPRISES PREPARING A TREATING SOLUTION BY ADDING A PHENOL TO AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION IN AN AMOUNT TO PRODUCE A SOLUTION CONTAINING FRO ABOUT 25 TO ABOUT 700 GRAMS OF PHENOL PER LITER OF SOLUTION AND CONTACTING SAID DISTILLATE WITH SAID SOLUTION. 